Sherlock Holmes sprang to his feet the moment that she was gone and rushed into his room.

He returned in a few seconds enveloped in an ulster and a cravat.

"I'll follow her," he said, hurriedly; "she must be an accomplice, and will lead me to him.

Wait up for me." The hall door had hardly slammed behind our visitor before Holmes had descended the stair.
Looking through the window I could see her walking feebly along the other side, while her pursuer dogged her some little distance behind.
"Either his whole theory is incorrect," I thought to myself, "or else he will be led now to the heart of the mystery." There was no need for him to ask me to wait up for him, for I felt that sleep was impossible until I heard the result of his adventure.
It was close upon nine when he set out.

I had no idea how long he might be, but I sat stolidly puffing at my pipe and skipping over the pages of Henri Murger's "Vie de Boheme." Ten o'clock passed, and I heard the footsteps of the maid as they pattered off to bed.